I know I used to have one back in the days of "classic" VB. It might have been part of a plugin to the IDE.
In the code editor you could put the cursor inside a function or procedure and click this toolbar button and it would pop up a list of all the places in your code that called the thing your cursor was in. Very useful when you have a lot of code.
I can't find it in VS2013.
Does it exist?